In contrast to conventional database management systems (DBMS), against which a query is generally executed once and returns a set of results for a given point in time, a data stream management system (DSMS) enables the execution of continuous queries against data streams, thus reacting over time to continuous inputs from different sources. A data stream management system may for instance be implemented in the form of a computer program.
Some existing data stream management systems are disclosed for instance in D. J. Abadi, D. Carney, U. Çetintemel, M. Cherniack, C. Convey, S. Lee, M. Stonebraker, N. Tatbul, and S. Zdonik, Aurora: A New Model and Architecture for Data Stream Management, VLDB Journal, 12(2), August 2003 (here referred to as reference [1]) and in Y. Bai, F. Wang, P. Liu, C. Zaniolo, and S. Liu, RFID Data Processing with a Data Stream Query Language, Proceedings of the 23rd International Conference on Data Engineering, ICDE 2007, pp. 1184-1193, 2007 (here referred to as reference [2]).
It is desirable to improve existing data stream management systems, including their efficiency and usability in operation, i.e. when data streams are already being received. It is desirable to do so without increasing, or at least without excessively increasing, the implementation and architecture complexity and the associated equipment costs.